chore: refactor packet registration

Author: kashike

proxy/src/main/java/com/velocitypowered/proxy/protocol/PacketMapper.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2018-2023 Velocity Contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.velocitypowered.proxy.protocol;
+
+import com.velocitypowered.api.network.ProtocolVersion;
+import org.jspecify.annotations.Nullable;
+
+interface PacketMapper {
+  default void readWrite(final int id, final ProtocolVersion from) {
+    this.readWrite(id, from, null);
+  }
+
+  void readWrite(final int id, final ProtocolVersion from, final @Nullable ProtocolVersion to);
+
+  default void writeOnly(final int id, final ProtocolVersion from) {
+    this.writeOnly(id, from, null);
+  }
+
+  void writeOnly(final int id, final ProtocolVersion from, final @Nullable ProtocolVersion to);
+}

proxy/src/main/java/com/velocitypowered/proxy/protocol/PacketMapping.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright (C) 2018-2023 Velocity Contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.velocitypowered.proxy.protocol;
+
+import com.velocitypowered.api.network.ProtocolVersion;
+import org.jspecify.annotations.Nullable;
+
+/**
+ * Packet mapping.
+ */
+public record PacketMapping(
+    int id,
+    ProtocolVersion from,
+    @Nullable ProtocolVersion to,
+    boolean writeOnly
+) {
+}